A slide from my talk today titled "standing on the shoulders of a giant GNOME" describing all the different components from the kernel and init, to thing like network manager, modemmanager dbus, a gnome-session, geoclue and lots more. Have a listen at around 23:40 in the recording for more intformation.
https://cdn.fosstodon.org/media_attachments/files/110/840/202/455/732/453/original/db500aecaa62ce61.png